1. Field of the Invention
The present invention relates to a data recording/reproducing apparatus, such as a hard disc drive (HDD).
2. Description of the Related Art
In a HDD, data heads and a servo head are arranged to face both surfaces of a plurality of recording mediums (discs). The data heads and servo head are simultaneously moved by a head drive mechanism, for seeking in a radial direction of the recording mediums. The servo head reads out servo data recorded on one surface of one of the recording mediums. On the basis of a servo signal output (read out) from the servo head, a servo system circuit enables the servo head to seek a destination track (cylinder) and positions the servo head to a center of the destination track. Following the servo head, the data heads are moved for seeking in the radial direction of the recording mediums and are brought to the centers of destination tracks. Data is recorded/reproduced by means of one of the data heads.
The position of each data head may be displaced relative to the position of the servo head, owing to a temperature change in the space where the HDD is installed. This undesirable phenomenon is called an "off-track phenomenon", or "thermal off-track phenomenon." If the off-track distance (positional displacement) of the data head increases up to about 10% to 15% of the width of a track, exact reproduction of data is made impossible.
In the prior art, when data is written or read, if thermal off-track exceeding a allowable off-track distance occurs, the off-track is corrected by means of a embedded servo system, or the combination of the embedded servo system and a dedicated servo system. Namely, the position of the data head is corrected. In this conventional method, however, a carriage supporting the data heads must be moved, though slightly. This increases time for head positioning, and lowers the throughput of the system using the HDD.